Multi-rotor turbine arranged for coordinated rotational speeds

Abstract

A wind turbine system is described comprising a plurality of wind turbine modules, each including a rotor, mounted to a support structure including a tower. In use, each rotor has an associated rotating unbalance that defines an unbalance vector. The wind turbine system includes control means configured to coordinate the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors. Also described is a method of controlling such a wind turbine system. The method comprises coordinating the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors.

The invention claimed is: 
     
       1. A wind turbine system comprising:
 a plurality of wind turbine modules mounted to a support structure including a tower, each of the plurality of wind turbine modules including a rotor, wherein, in use, each rotor has an associated rotational imbalance; and 
 a control system comprising a processor, the control system configured to:
 determine, for each rotor, a respective imbalance vector corresponding to the associated rotational imbalance; and 
 based on a comparison of the respective imbalance vectors, coordinate the rotational speeds of the rotors to attenuate oscillations of the support structure caused by the rotational imbalances associated with the rotors. 
 
 
     
     
       2. The wind turbine system of  claim 1 , wherein coordinating the rotational speeds of the rotors comprises:
 coordinating the rotational speeds of a first rotor and a second rotor such that an angle between the imbalance vector of the first rotor and the imbalance vector of the second rotor varies. 
 
     
     
       3. The wind turbine system of  claim 2 , wherein coordinating the rotational speeds of the rotors comprises controlling the rotational speed of the first rotor to be different from the rotational speed of the second rotor. 
     
     
       4. The wind turbine system of  claim 3 , wherein the rotational speed of the first rotor is less than 98 percent of the rotational speed of the second rotor. 
     
     
       5. The wind turbine system of  claim 4 , wherein the rotational speed of the first rotor is more than 90 percent of the rotational speed of the second rotor. 
     
     
       6. The wind turbine system of  claim 3 , wherein coordinating the rotational speeds of the rotors further comprises controlling the rotational speed of the second rotor. 
     
     
       7. The wind turbine system of  claim 3 , wherein coordinating the rotational speeds of the rotors comprises controlling the rotational speed of the first rotor to be different from a rotational speed of at least a third rotor of the wind turbine system. 
     
     
       8. The wind turbine system of  claim 1 , wherein coordinating the rotational speeds of the rotors comprises controlling the first rotor and the second rotor to achieve a target angular difference between an azimuth position of the first rotor and an azimuth position of a second rotor. 
     
     
       9. The wind turbine system of  claim 8 , further comprising:
 a sensor configured to detect vibrations within the support structure, 
 wherein the control system is further configured to vary the target angular difference in dependence on a magnitude of the detected vibrations. 
 
     
     
       10. The wind turbine system of  claim 8 , wherein the the target angular difference corresponds to a non-zero angle between the imbalance vectors of the first rotor and the second rotor. 
     
     
       11. The wind turbine system of  claim 10 , wherein the target angular difference corresponds to an angle between 90 degrees and 240 degrees. 
     
     
       12. The wind turbine system of  claim 11 , wherein the target angular difference corresponds to an angle of 180 degrees. 
     
     
       13. A method of controlling a wind turbine system comprising a plurality of wind turbine modules mounted to a support structure including a tower, each of the plurality of wind turbine modules including a rotor, wherein, in use, each rotor has an associated rotational imbalance, the method comprising:
 determining, for each rotor, a respective imbalance vector corresponding to the associated rotational imbalance; and 
 based on a comparison of the respective imbalance vectors, coordinating the rotational speeds of the rotors to attenuate oscillations of the support structure caused by the rotational imbalances associated with the rotors. 
 
     
     
       14. The method of  claim 13 , wherein coordinating the rotational speeds of the rotors comprises:
 coordinating the rotational speeds of a first rotor and a second rotor such that an angle between the imbalance vector of the first rotor and the imbalance vector of the second rotor is continuously varying. 
 
     
     
       15. The method of  claim 14 , wherein coordinating the rotational speeds of the rotors comprises controlling the rotational speed of the first rotor to be different from the rotational speed of the second rotor. 
     
     
       16. The method of  claim 13 , wherein coordinating the rotational speeds of the rotors comprises controlling the first rotor and the second rotor to achieve a target angular difference between an azimuth position of the first rotor and an azimuth position of a second rotor. 
     
     
       17. The method of  claim 16 , further comprising:
 detecting vibrations within the support structure; and 
 varying the target angular difference in dependence on a magnitude of the detected vibrations. 
 
     
     
       18. The method of  claim 16 , further comprising:
 setting the target angular difference to correspond to a 180 degree angle between the imbalance vectors of the first rotor and the second rotor. 
 
     
     
       19. A controller for a wind turbine system comprising a plurality of wind turbine modules mounted to a support structure including a tower, each of the plurality of wind turbine modules including a rotor, wherein, in use, each rotor has an associated rotational imbalance, wherein the controller comprises:
 a processor; and 
 a memory includes a set of program code instructions which when executed by the processor, perform an operation comprising:
 determining, for each rotor, a respective imbalance vector corresponding to the associated rotational imbalance; and 
 based on a comparison of the respective imbalance vectors, coordinating the rotational speeds of the rotors to attenuate oscillations of the support structure caused by the rotational imbalance associated with the rotors. 
 
 
     
     
       20. A computer program product comprising a non-transitory computer-readable medium, the computer-readable medium comprising program code instructions which, when executed by one or more processors, perform an operation for controlling a plurality of rotors mounted to a support structure including a tower, each rotor having an associated rotational imbalance, the operation comprising:
 determining, for each rotor, a respective imbalance vector corresponding to the associated rotational imbalance; and 
 based on a comparison of the respective imbalance vectors, coordinating the rotational speeds the rotors to attenuate oscillations of the support structure caused by the rotational imbalance associated with the rotors.